This application claims priority to an application entitled xe2x80x9cDevice and Method for Performing Inter-MSC Soft Hand-off Using Router in CDMA Communication Systemxe2x80x9d filed in the Korean Industrial Property Office on Mar. 15, 1999 and assigned Ser. No. 99-8561.
1. Field of the Invention
The present invention relates generally to a device and method for performing an inter-MSC (Mobile Switching Center) soft hand-off using a router in a CDMA communication system, and in particular, to a device and method for performing a soft hand-off between the cells, each belonging to different mobile switching centers, using a router in a CDMA communication system.
2. Description of the Related Art
In a CDMA (Code Division Multiple Access) system, when a mobile station (MS) travels from one cell area to the adjacent cell area during a call connection, the base station controller (BSC) of an anchor side determines whether to perform a hand-off based on the pilot strength measurement message (PSMM) received from a mobile station (MS). When the hand-off is required, the base station controller performs a hard-hand-off.
To this end, a vocoder of the anchor side releases the communication path, and the base station controller of a new cell allocates a new vocoder to set another communication path to complete the hand-off. In the process of switching to another vocoder, the mobile station experiences speech interruption in the communication channel. Moreover, the call drop rate in the hard hand-off is relatively higher than that of the soft hand-off.
It is, therefore, the object of the present invention to provide a device and method for performing a soft hand-off when a mobile station requires the hand-off while traveling from one cell to another cell, thereby preventing speech interruption due to the switching of the vocoder between the cells of a CDMA communication system.
To achieve the above object, there is provided a method for performing an inter-MSC (Mobile Switching Center) soft-hand-off (IMSHO) using a router in a code division multiple access (CDMA) communication system. The method includes the steps of transmitting a pilot strength measurement message (PSMM) from a mobile station (MS) of the anchor side to a transcoder and selector bank (TSB) of the anchor side; transmitting a hand-off request message from the TSB of the anchor side to a call control processor (CCP) of the anchor side; transmitting an IMSHO request message from the CCP of the anchor side to a CCP of the target side; transmitting a hand-off request message from the CCP of the target side to an BTS (Base station Transceiver System) control processor (BCP) of the target side; transmitting an TCE (Traffic Channel Element) allocation request message from the BCP of the target side to a channel element (CE) of the target side; transmitting a TCE allocation response message from the CE of the target side to a BCP of the target side; transmitting a hand-off allocation response message from the BCP of the target side to an CCP of the target side; transmitting an IMSHO allocation response message from the CCP of the target side to the CCP of the anchor side; transmitting a hand-off allocation response message from the CCP of the anchor side to the TSB of the anchor side; transmitting a soft hand-off operation message from the TSB of the anchor side to a CE of the anchor side; transmitting a response control message from the CE of the anchor side to the TSB of the anchor side; transmitting a time sync message from the TSB of the anchor side to the CE of the target side; transmitting the time sync message from the CE of the target side to the TSB of the anchor side; transmitting a time sync completion message from the CE of the target side to the BCP of the target side; transmitting a soft hand-off active message from the CE of the anchor side to the BCP of the anchor side; transmitting a hand-off direction message (HDM) from the TSB of the anchor side to the mobile station (MS) of the anchor side; transmitting an MS reception message from the TSB of the anchor side to the CE of the target side; transmitting an MS reception response message from the CE of the target side to the TSB of the anchor side; transmitting a hand-off completion message (HCM) from the mobile station of the anchor side to the TSB of the anchor side; and, transmitting a hand-off notice message from the TSB of the anchor side to the CCP of the target side.
In addition, there is provided a device for performing an IMSHO using a router in a CDMA communication system. The device comprises a router module allocated to each mobile switching center in the CDMA system, the router module for interfacing with a global communication interconnection network (GCIN); a base station subsystem (BSS) provided in each mobile switching center which is connected to the router module and includes the GCIN; a base station modulator connected to the GCIN in the BSS, for providing the link configuration information of the router module; and a trunk for connecting the router modules of different mobile switching centers to enable the communication between the base station subsystems belonging to the different mobile switching centers.